1. Field of the Invention
This invention relates to a tape transport and guide structure for a video cassette recorder (VCR), which transports a tape and positions a drum in a tape loading and unloading apparatus of the VCR, which transfers the tape in a cassette to bring it into and out of engagement with the drum.
2. Description of the Prior Art
Generally, a drive mechanism of a tape loading and unloading apparatus which brings a tape for a video cassette recorder(VCR) into and out of engagement with a drum is of any one of two types: a ring type utilizing two rotary rings and a cam type utilizing cams. The conventional tape loading apparatus of a VCR deck, which has the ring type drive mechanism commercially available from Gold Star Co., Ltd. in Korea, under Model NO. GS-CIP is in the form as shown in FIGS. 3 to 5 of the accompanying drawings, which comprises a pair of slant bases (2) each having a guide roller(1) and disposed on a guide rail(4) for movement along a pair of guide grooves(3) of the rail, V-shaped stoppers(5) functioning to stop the movement of the slant bases(2) along the guide grooves(3), thereby determining a final position of the tape, a drum base (not shown in FIG. 3 because it is located under a drum(6) slantly supporting the drum(6) at an incline of a given angle, a main slant post(7) turning round the drum, and a main slant post stopper(8) having a stopping groove (8a) for receiving the main slant post(7). In addition, a pair of support shafts (9a, 9b) defining a reference plane for a cassette are fixedly mounted on a main base of the deck, on which the drum base is disposed, at positions adjacent to the tape supply and take-up reels, respectively.
With the construction having such principal elements, as can be seen in FIG. 4 showing a tape transport system, the tape(10) is brought into engagement with the drum(6) by the movement of the guide rollers(1) mounted on the slant bases(2) from stationary positions shown in FIG. 3 to positions in FIG. 4 along the guide grooves(3) of the guide rail(4) and the movement of the main slant post(7) round the drum. In this loaded state, a picture can be recorded on the tape through the drum, or a picture previously recorded on the tape may be played back.
At this point, the turning movement of the main slant post causes the tape to be passed through the drum at a given angle which is kept in a vertically oriented posture by means of a main slant post turning mechanism as shown in FIG. 5. More specifically, when the driving force of a loading motor (not shown) is transmitted to a loading gear(11), the gear rotates a cam gear(13) through a connecting gear(12) interposed between them. At this time, since a pin(17) of a lever cam(14) is received in a curved groove (13a) formed in the cam gear(13) to be slidingly movable along the groove, the rotation of the loading gear(11) leads to counterclockwise rotation of a lower toothed end(14a) of the lever cam(14) through a series of gears comprising the loading gear(11), the connecting gear(12), the cam gear(13) and the lever cam (14), thereby resulting in clockwise rotation of a gear(16) of a post arm(15), which is engaged with the toothed end(14a). As a result, the post arm(15) is rotated from a position as indicated by the two-dot-and-dash lines in FIG. 5 to a position as indicated by the solid line, so that the main slant post (7) fixed to a free end of the post arm(15) is moved toward and received in the stopping groove(8a) of the main slant post stopper(8), thereby guiding the travel of the tape.
During the turning movement of the main slant post, a pair of the slant bases(2) movable along the guide grooves(3) are also moved from a stop position of the guide rail as shown in FIG. 3 to a position of the V-shaped stopper mounted on the drum base along a pair of the semicircular guide grooves (3) formed in the guide rail(4) by means of a loading mechanism (not shown), whereby the guide rollers(1) on the slant bases(2) bring the tape into engagement with the drum(6). The other of the V-shaped stoppers (5) functioning to stop the movement of the slant bases is not shown in FIG. 3 because it is positioned behind the drum(6).
In the cam type drive mechanism (commercially available from SONY Company in Japan, under Model No. TR-55) other than the above described ring type drive mechanism acting to load the tape by means of the rotary ring gear, the basic operation of loading and unloading the tape us substantially the same as that of the ring type. The cam type is, however, different from the ring type in that the former utilizes a cam gear and a folding lever for moving the slant bases so as to engage the tape with the drum, in place of the ring gear of the latter. In addition, the cam type drive mechanism does not carry out the turning movement of the main slant post by the post turning mechanism as described above, but utilizes a main slant post fixedly mounted at a given angle and a separate tape guide roller movable along a guide groove formed in a guide rail in order to permit the tape passed through the main slant post via the guide roller to be maintained in a vertically oriented posture.
As described above, both the ring type and cam type drive mechanisms are complex in construction, requiring a plurality of parts. More particularly, the ring type drive mechanism comprises a plurality of parts, such as the guide rail for guiding the moving slant bases, the drum base for mounting the drum, the V-shaped stoppers, the movable main slant post, the support shafts for supporting the cassette, and the main slant post turning device, all of the them being mounted on a main base, while the cam type drive mechanism comprises a plurality of parts, such as the guide rail for guiding the moving slant bases, the stoppers mounted on the guide rail, the drum base for mounting the drum, the fixedly mounted main slant post, and the tape guide roller movable on the guide rail, all of them being individually mounted on a main base. As a result, finishing and assembly errors of the respective parts may adversely affect stability of the entire tape transport system and product quality. Further, the requirement for a plurality of the elements results in complicated, tedious assembly work and lower manufacturing efficiency.